Rare Etiology of Isolated Macrocytosis: Adenosine Kinase Deficiency With a Novel Mutation.

Adenosine kinase (ADK) deficiency is an autosomal recessive disorder characterized by psychomotor developmental delay, epilepsy, dysmorphic features, and liver disease. It is a rare inborn error of methionine and adenosine metabolism. The diagnosis is based on clinical findings, laboratory findings, and molecular analysis of the ADK gene. A novel homozygous mutation NM_006721.4 c.515A>C (p.Asn172Thr) in the ADK gene associated with hypermethioninemia due to ADK deficiency was detected by whole-exome sequencing in a 7-year-old girl who had reticulocytosis, hyperbilirubinemia, elevated mean corpuscular volume, and without mental-motor developmental delay. ADK deficiency as a metabolic disease should be considered in the differential diagnosis of patients with isolated macrocytosis, even without neurologic delay.